For use in rooms of varying areas, conventional common air conditioners are prepared as classified according to the maximum operating capacity into different types corresponding to several categories into which the room areas are classified. For installation in an actual room, an air conditioner of particular type is selected which corresponds to the category in which the area of that room belongs. Thus, air conditioners of the same type are selected for rooms of different areas if the room areas are within a category.
However, these conventional air conditioners are controlled in the same way despite the difference in room area if the room areas are within the same category, so that the indoor spaces are not always air-conditioned comfortably, for example, owing to an excessive or insufficient amount of air flow. Further even if the room area is in match with the operating capacity, the indoor conditions vary depending on the number or position of occupants, whereas the air conditioner is not controlled in accordance with such variations.
As disclosed in Unexamined Japanese Patent Publication HEI 2-10045, therefore, a system has been proposed which comprises a CCD or like solid image pickup device and an ultrasonic sensor for detecting indoor conditions to automatically air-condition the indoor space according to the detected result.
With this conventional system, indoor image data is fed to a memory from the CCD in advance, and when persons have entered the room, the number of occupants of the room is detected from the difference between the image data then obtained and the stored image data. The distance to the occupants is detected from signals from the ultrasonic sensor. The operating capacity or amount of air flow is controlled in accordance with the indoor conditions detected.
The conventional system requires not only a complex peripheral circuit for the image processing of output of the CCD but also a circuit for causing the ultrasonic sensor to scan the entire interior of the room. The arrangement for detecting the indoor conditions is therefore extremely complex to entail the problem of making the overall system large-sized. Moreover, the measurement of distances by the ultrasonic sensor involves great errors.
On the other hand, a system has been proposed for measuring the distances to articles by resorting to scanning with a light beam and the principle of triangulation as disclosed in Unexamamined Japanese Patent Publication HEI 2-276908. This measuring system has a light detecting surface comprising a PN junction face and employs a position sensitive light detector for outputting a signal corresponding to the position of a spotlight incident on the light detecting surface. The system gives measurements with higher accuracy than the ultrasonic sensor which affords distance measurements. The measuring system nevertheless has the problem of being unable to measure the interior area of rooms or the number of occupants and needing a scanning circuit.